For more than three decades scholars have debated about if, when, and under what circumstances religiosity deters delinquency. The present study uses multilevel modeling data analytic techniques (i.e., hierarchical linear model [HLM]) and large nationally representative samples of American public high schools (N = 227) and high school seniors ( N = 16,595) to examine various unresolved issues in the ongoing debate, with a specific focus on the relationships between individual- and contextual-level (i.e., school) religiosity and adolescent's use of tobacco, alcohol, and marijuana. The results indicate first, that the higher adolescents' level of religiosity, the less likely they are to be current tobacco users, to engage in binge drinking, or to have used marijuana in the past year; second, that as the level of religiosity in a school increases, adolescents' frequency of cigarette use, binge drinking, and marijuana use decreases; third, that the religiosity of the school influences students' substance use, over and above their individual religiosity, but that this relationship exists only for marijuana; and fourth, that the strength of the relationship between individual- level religiosity and individual- level substance use varies depending upon the religiosity of the context, such that adolescents who are highly religious and in highly religious contexts are less likely to engage in binge drinking or marijuana use than those who are equally religious but in less religious contexts. Future research should seek to understand the mechanisms through which individual- and contextual-level religiosity influences young people's use of substances and other delinquent behaviors.